Journal of Mechanical Engineering, Automation and Control Systems
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On the issue of the motion of balls in a double pendulum
Get PDFThe paper considers a model of a vertical double pendulum with one suspension centre moving in a vertical plane. For the proposed system of pendulums, differential equations of motion and conditions for the collision of balls are obtained. When modelling the movement of pendulums, the central impact of the balls was considered for various variants of the movement of the suspension point: the suspension point oscillates in the vertical direction; the suspension point makes rotational movements in the vertical plane. In this case, various conditions of the central impact between the balls were considered: absolutely inelastic impact; absolutely elastic impact; impact with the transformation of impact energy (elastic impact). Comparison of the results of the numerical simulation and the results of experiments with the Kapitza pendulum in published sources confirmed the possibility of modelling an elastic impact between balls in a double pendulum and between balls in an autobalancer with a horizontal axis of rotation of the rotor
Genetic engineering – construction of a network of arbitrary dimension with periodic attractor
Get PDFIt is shown, how to construct a system of ordinary differential equations of arbitrary order, which has the periodic attractor and models some genetic network of arbitrary size. The construction is carried out by combining of multiple systems of lower dimensions with known periodic attractors. In our example the six-dimensional system is constructed, using two identical three-dimensional systems, which have stable periodic solutions
Recycling technology of old cement concrete pavement in highways
Get PDFThrough the practice of a highway pavement overhaul project, the feasibility of the old concrete pavement recycling scheme in terms of technology, economy and sustainable development is analyzed. The dynamic characteristics of concrete pavement were tested. The results show that crushing the old concrete panels into recycled aggregates and then re-use them not only eliminates the negative impact on the ecological environment caused by the land occupation of waste aggregates and needs to be disposed of, but also promotes the recycling of engineering waste and reduces the project cost. The pavement paved with recycled cement concrete can basically achieve the same dynamic performance as the pavement paved with conventional concrete
Optimization on the jet characteristics of the main nozzle of hot-blowing snow removal device
Get PDFThe exhaust devices used by snow removal vehicles are mainly based on hot-blowing snow removal. Due to the inherent characteristics of the turbojet engine such as low flow rate and high exhaust temperature, the modified hot-blowing snow removal device has problems of low snow removal efficiency and the possibility of ablation and damage to the road surface. In order to solve the problem, transforming the turbofan engine with a high flow rate and a low exhaust temperature into a hot-blowing snow removal device is an important improvement to achieve efficient and safe snow removal operations. In order to convert a medium bypass ratio turbofan engine into a hot-blowing snow removal device, the computational fluid dynamics (CFD) software CFX was used to analyze the internal and external flow field characteristics of the main nozzle of an exhaust device under the 60 % rated condition of the engine. The effective area sizes of the jet velocity and temperature predicted by the external flow field were used to optimize the layout of the main nozzle
Railway foreign body vibration signal detection based on wavelet analysis
Get PDFBased on the wavelet packet analysis method with time-frequency analysis characteristics, the measurement signal of the vibration system is processed for noise reduction, the soft-hard threshold compromise wavelet denoising method used has the advantages of soft threshold and hard threshold denoising, and through the introduction of compromise factors, signal processing can be performed more flexibly in signal analysis. For the denoised signal, the fundamental wavelet time-energy spectrum analysis, the main components of the signal can be clearly displayed, and according to the distribution of its energy in each frequency band, the signal characteristics can be displayed intuitively. Experimental results show: It can be determined that there is a foreign body intrusion incident at a position 520 m away from the monitoring point, rather than a normal train travel incident. In fact, we are walking back and forth at a distance of about 520 m from the monitoring point, simulating the intrusion of illegal foreign objects such as pedestrians and livestock beside the railroad tracks prove that analysis and judgment can be known, the wavelet analysis proposed by the author can realize the monitoring and judgment of some illegal foreign body intrusion incidents such as pedestrians and livestock
Analysis of electromagnetic characteristic in the interior permanent magnet brushless DC motor
Get PDFThe motor vibration is mainly induced by the electromagnetic excitation. In order to improve the running performance of the permanent magnet brushless DC motor (BLDCM) within the rolling rotor compressor, this paper builds the predicted model of the electromagnetic excitation and analyzes the electromagnetic characteristic of the BLDCM. Firstly, the electromagnetic field is divided into four regions in 2D plane, including the magnet, air gap, stator slot, and slot-opening subdomains. Then, the relative equations of the electromagnetic field are constructed, and the vector magnetic potential is solved by the variable separation method. Thus, the magnetic flux density of the air gap is derived by the corresponding vector magnetic potential, which is used to describe the electromagnetic excitation. Based on the built model, the effects of the slot opening and air gap length on the electromagnetic characteristic are analyzed. The analysis results can provide a reference for the improvement of the electromagnetic characteristic of the BLDCM by structure optimization
Influence of floating support on the dynamic characteristics of compound planetary gear set
No full textDue to a large number of components, complex meshing relations and high requirements for assembly accuracy, the dynamic characteristic of compound planetary gear, such as vibration, impact, periodic motion and load sharing, are more easily affected by internal excitation than those of simple planetary gear set and parallel shafting gear set. To improve the load sharing behavior and the resistance of Chaos motions in the compound planetary gear set, in this work, by introducing the floating support into the center gear and planet gear, a lumped-parameter dynamic model of the compound planetary gear set is built based on the lumped parameter method and Lagrange kinematics equation. The steady response is calculated by numeric method to investigate the influence of floating support from different components on loading sharing behavior and periodic motion. The results indicate that, the increase of the floating value of all components improves the instantaneous load-sharing behavior, and single floating of planet gear reduces the load sharing behavior. To avoid the system being in quasi-periodic motion and Chaos motions under the condition of floating support, the input speed should be avoided away from the range of 3201 r/min-5069 r/min
Diagnosis and analysis of electric power steering rattle noise based on multiple coherence method
Get PDFElectric power steering (EPS) system is becoming the primary source of Electric Vehicle (EV) noise due to absence of classic power train. The rattle noise produced by EPS, which is easily discernible when driving. Since the conventional subjective evaluation approach makes it difficult to identify the source, it is required to establish an objective way to solve such an issue. In this paper, the principle of multiple coherence method is first addressed analytically, and then is employed to analyze the vibration signal acquisition from EPS different points, meanwhile, combine with in-car sound signal, to accurately identify the specific location
The longitudinal vibration characteristics and parametric analysis of a ship thrust bearing integrated with internal disc springs
Get PDFTo reduce the transmission of shafting longitudinal vibration in surface ships, a design of thrust bearing integrated with internal disc springs is proposed and the longitudinal vibration characteristics of the shafting are studied. According to the structural characteristics of thrust bearing and the deformation characteristics of disc springs, the specific size and combination forms of disc springs in the thrust bearing are designed, and the effective disc springs schemes are achieved according to the static and dynamic design requirements. With the integration of the disc springs into the thrust bearing, the peak of longitudinal displacement response at the base of thrust bearing can be reduced by 10 dB by two schemes of disc springs. The proposed design can effectively suppress the transmission of shaft longitudinal vibration to the hull, which has engineering significance for the longitudinal vibration control of the shafting of the surface ship
Effect of material characteristics of explosive on formation of collinear explosively formed projectile from warhead with double layer liners
Get PDFIn order to obtain the effect of material characteristics of explosive on the formation of collinear explosively formed projectile (EFP)from warhead with dosuble liners, the LS-DYNA simulation software was used to simulate and analyze the forming process of collinear EFP from warhead with five explosive materials including pe4booster, PETN, TNT, C4 and B explosives. The results indicate that with the increase of density, detonation velocity, and detonation pressure, the velocity and the length diameter ratio of the front EFP and rear EFP increase with different laws. With the increase of explosive material density, the velocity and the length diameter ratio of EFPs increase gradually, but the increasing rate decreases gradually. As the detonation velocity increases, the velocity of EFPs increase gradually, but the increasing rate decreases gradually. The length diameter ratio of EFPs decreases first and then increases gradually, showing an "s"-shaped change law. With the increase of explosive detonation pressure, the velocity of EFPs increase gradually, but the increasing rate decrease gradually. The length diameter ratio of the front EFP shows a parabolic growth law with the increase of detonation pressure, and the length diameter ratio of the rear EFP shows an "s"-shaped change law with the detonation pressure